The present invention relates to an optical system and an optical apparatus, and more specifically to an optical system which is favorably used, for example, as a projection optical system used for a projection display apparatus or an imaging optical system used for a digital camera, video camera, or the like, and an optical apparatus equipped with the optical system.
Recently, the market for projection display devices has been expanding significantly with a wide spread use of personal computers. As a light valve that performs optical modulation in a projection display device, a transmissive or reflective liquid crystal display device, a digital micromirror device (DMD®) having micromirrors disposed regularly, and the like are known. Among them, the DMD device using micromirrors is suitable for downsizing, as it has a high response speed and allows for a configuration in which illumination light of each of three primary colors of light is sequentially projected on a single-plate light valve in time division.
Along with an increase in demand for mobile applications, small projection display devices are required, and it is preferable, for that purpose, to use a projection optical system configured compact with a less number of lenses. Further, downsizing is also required for digital cameras, video cameras, and the like, as well as for imaging optical systems used for these. For optical systems composed of six lenses as a whole, those described, for example, in Japanese Unexamined Patent Publication No. 2000-039555 and Japanese Unexamined Patent Publication No. 2(1990)-040607 are known.